CMS integration is connecting the signage or video platform to a system that already owns your content or data, so nothing has to be maintained in two places. The other system might be a web CMS, a PIM, a menu-management platform, a DAM or the till.
The reason to bother is drift. Every duplicate copy of a price, an opening time or a product photo will eventually disagree with the original, and the screen is the copy nobody thinks to update. Integration makes the screen a view of the source rather than a second version of it.
The caveat is that integrations are easy to build and hard to own. The question is not whether it can be connected but who fixes it when the source system changes a field name during an upgrade, usually with no notice, and usually first noticed by a customer looking at a screen showing nothing.
Prefer integrations that fail visibly and degrade gracefully: a zone that hides itself and raises an alert beats one that renders an empty template. And agree up front which team owns the connection, because "the signage vendor" and "the platform team" both reliably assume it is the other.